From owner-freebsd-questions Fri Jul 7 20:27:20 2000 Delivered-To: freebsd-questions@freebsd.org Received: from psasolar.colltech.com (psasolar.colltech.com [208.229.236.14]) by hub.freebsd.org (Postfix) with ESMTP id B775C37B5B3 for ; Fri, 7 Jul 2000 20:27:16 -0700 (PDT) (envelope-from jmutter@colltech.com) Received: from localhost by psasolar.colltech.com (8.9.3/8.9.3/not) with ESMTP id WAA28367; Fri, 7 Jul 2000 22:27:10 -0500 (CDT) Date: Fri, 7 Jul 2000 22:27:10 -0500 (CDT) From: "James A. Mutter" X-Sender: jmutter@psasolar.private.psa.pencom.com To: Emmanuel Gravel Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Performance issues with dd In-Reply-To: <3966991C.7BB8086A@earthlink.net> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > As a backup measure, I'm using two hard drives of the same size, > but only mounting one, and I have a cron job that dd's one to > the other every night. The drives are 18 GB U160 SCSI, on a > AHA-29160N. The whole process takes 45 minutes. A quick calc > tells me it should be finished at best in 2 minutes, at peak > rate. This is over a 20x difference. > > Does anyone have any idea why it's taking so long? Is it just > dd that's the problem? The CPU is a PIII 650, and there's more > than enough memory to go, so I don't think the CPU would be > any kind of an impact here. Is there a better app out there > to do the job? I'm dumping one full raw device to the other, > not individual partitions. Could that be another problem? > Since you're duplicating an entire disk why not try RAID 0? It's probably a better solution than "dd" and will keep you spare as current as possible. As far as "dd" goes, consider ditching it and using dump/restore, pax, or tar. You may not know it, but "dd" is duplicating the entire disk, bad sectors and all. Good luck, Jim To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message